Sepiolite
| Sepiolite | |
|---|---|
 |
|
| General and classification | |
| other names |
Meerschaum |
| chemical formula | Mg 8 [(OH) 2 | Si 6 O 15 ] 2 • (4 + 8) H 2 O |
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.EE.25 ( 8th edition : VIII / H.33) 74.03.01b.01 |
| Similar minerals | alabaster |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Room group (no.) | Pncm (No. 52) |
| Lattice parameters | a = 13.405 Å ; b = 27.01 Å; c = 5.2750 Å |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 2 to 2.5 |
| Density (g / cm 3 ) | measured:> 2 (dry, porous masses float on water); calculated: 2.26 |
| Cleavage | uneven |
| Break ; Tenacity | nd |
| colour | white, gray-white, yellowish-white |
| Line color | White |
| transparency | opaque to slightly translucent |
| shine | matt greasy shine |
| Crystal optics | |
| Refractive indices |
n α = 1.498 to 1.522 n β = 1.507 to 1.553 n γ = 1.527 to 1.579 |
| Birefringence | δ = 0.029 to 0.057 |
| Optical character | biaxial negative |
| Axis angle | 2V = 20 to 70 °; calculated: 18 ° |
The mineral sepiolite , also commonly known as meerschaum , is a seldom occurring magnesium silicate with the chemical composition Mg 8 [(OH) 2 | Si 6 O 15 ] 2 · (4 + 8) H 2 O. According to its crystal structure, it belongs to the layered silicates . It crystallizes in the orthorhombic crystal system and has so far only been found in the form of earthy or massive, bulbous, rarely also fine-fiber mineral aggregates of white, gray-white or yellowish-white color.
Not to be confused with the mineral, the plant Seemoos , which is also known as sea foam.
Etymology and history
The name Meerschaum was coined by Abraham Gottlob Werner in 1788 and is the literal translation of the Latin name spuma maris , which alludes to the soapy, porous nature of the stone.
The scientific name sepiolite was coined by Ernst Friedrich Glocker in 1847 and is the Greek name for sepia stone. This name alludes to the calcareous Schulp of the Sepia, which, like meerschaum, is light and porous.
The old magnesite quarry "Bettolino" in the Italian municipality of Baldissero Canavese (Piedmontese : Bausser ) has been considered the type locality since 1847 .
classification
In the meantime outdated classification of minerals by Strunz (8th edition) of sepiolite is part of the general department of " phyllosilicates (phyllosilicates)". With the revision of Strunz's mineral classification in the 9th edition , this section was also subdivided more precisely according to the structure of the connection and the mineral is now accordingly in the subdivision of “Simple tetrahedral networks made of 6-membered rings, connected by octahedral networks or bands ".
The systematics of minerals according to Dana , which is common in the English-speaking world , assigns sepiolite to the division of " layered silicates: modulated layers with connected stripes " and there together with falcondoite and loughlinite in the "palygorskite-sepiolite group (sepiolite subgroup)".
Crystal structure
Sepiolite crystallizes orthorhombically in the space group Pncn (space group no. 52) with the lattice parameters a = 13.405 Å ; b = 27.016 Å and c = 5.2750 Å as well as four formula units per unit cell .
properties
Theoretically, based on the possible packing density of the unit cell , sepiolite has a density of 2.26 g / cm³. However, the mineral is often very porous, so, like pumice , it contains a lot of air, which can reduce its density to the point where it becomes buoyant.
Before drying, the meerschaum tuber is soft and greasy to the touch. When it comes into contact with water, it foams like soap and was therefore used by the Greeks for cleaning purposes. This tuber is ideal for making pipes, as it is easy to work with and very absorbent due to its porous structure. The mouthpiece is made of different materials, however, as the tongue would stick to sepiolite.
Education and Locations
Sepiolite is formed hydrothermally by converting serpentinite . Accompanying minerals include dolomite , loughlinite , magnesite , montmorillonite , opal , palygorskite and serpentinite.
As a rather rare mineral formation, sepiolite can sometimes be abundant at different sites, but overall it is not very common. Around 200 sites are known to date (as of 2013). In addition to its type locality "Bettolino", the mineral occurred in Italy in other places in the Canavese region (Piedmont), at the mine on Schneeberg (Miniera Monteneve) in the Passeier Valley (Trentino-Alto Adige), near Serrazzano in the municipality of Pomarance (Tuscany) as well at some sites in the province of Vicenza (Veneto).
Among the classic localities, however, Turkey, specifically the one province of Eskişehir with their tertiary clay - deposits . Another well known deposit of sepiolite is in Tanzania . This is known as “Amboseli meerschaum” and is several million years younger than its Turkish relative. "Amboseli-Meerschaum" is heavier, usually more coarsely structured and has a gray tint.
In Germany, the mineral has so far been found at Peterleinstein near Kupferberg and in the “Heß” quarries near Wurlitz (Rehau) and “Haidberg” near Zell in Bavaria, at Rother Kopf near Gerolstein in the Rhineland-Palatinate Volcanic Eifel and at Schneeberg in the Saxon Ore Mountains .
In Austria, sepiolite could be found on the Hüttenberger Erzberg and the Millstätter Alpe in Carinthia, on the Totenkopf in the Salzburg Hohe Tauern and in several places in Lower Austria and Styria .
The only known site in Switzerland so far is Ronco Bedretto in the canton of Ticino.
Other locations are in Australia, Brazil, China, the Dominican Republic, France, Greece, Greenland, Indonesia, Israel, Japan, Canada, Kenya, Colombia, Madagascar, Malaysia, Mexico, Morocco, Norway, Poland, Romania, Russia, Sweden, Slovakia, Somalia, Spain, South Korea, Czech Republic, Hungary, Venezuela, the United Kingdom (Great Britain) and the United States of America (USA).
use
Sepiolite is mainly mined for the production of meerschaum pipes . But it is also used to make jewelry such as bracelets, necklaces and other things.
Vienna used to be the metropolis of meerschaum pipe production, well-known manufacturers are Andreas Bauer, Leopold Weiss and Strambach. But also in Ruhla in Thuringia special meerschaum pipes were made as early as the 19th century and these were sold worldwide. Evidence of this is now stored in the Ruhla Pipe Museum.
The economic situation in Turkey has meant that meerschaum can no longer be exported as a raw material. It has to be made into pipes or jewelry in Turkish workshops. Only so-called semi-finished products are allowed to leave the country in order to be provided with a mouthpiece and polished in other countries.
Pressed meerschaum pipes (massa meerschaum or Viennese meerschaum) are made from ground meerschaum (mostly from incorrect production or leftovers), lime and binding agent. Small pieces of meerschaum are also used instead of the more common activated carbon to make pipe filters . Due to its porous structure, it also absorbs liquids very well and is therefore also used as cat litter . Another application of so-called meerschaum dust is the removal of grease stains in the home.
See also
literature
- EF Glocker: Ordo XIII. Argillitae. II. Argillitae pingues. 15. Sepiolithus. In: Generum et Specierum Mineralium, Secundum Ordines Naturales Digestorum Synopsis. Apud Eduardum Anton, 1847, pp. 185–195 ( rruff.info PDF; 540.6 kB).
- Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Enke, 1978, ISBN 3-432-82986-8 , pp. 765 .
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel-Verlag, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 260 .
- Walter Schumann: Precious stones and gemstones . 13th edition. BLV, Munich / Vienna / Zurich 2002, ISBN 3-405-16332-3 , p. 248 (first edition: 1976).
Web links
- Mineral Atlas: Sepiolite (Wiki)
- WE Petrascheck: The meerschaum deposits near Eskişehir (PDF 80.2 kB)
Individual evidence
- ^ A b Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 682 .
- ↑ a b c Webmineral - Sepiolite.
- ↑ a b c American Mineralogist Crystal Structure Database - Sepiolite. (English, 2007)
- ↑ Sepiolite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001 ( handbookofmineralogy.org PDF; 72.8 kB).
- ↑ a b c Mindat - Sepiolite.
- ↑ See Meerschaum at Duden online
- ↑ Mineralienatlas: Bettolino type locality.
- ↑ Mindat - Number of localities for sepiolite.
- ↑ Find location lists for sepiolite in the Mineralienatlas and Mindat .